Q: What is your opinion on the much-advertised replacement roofs for conservatories? My wife wants to invest in one but I have my doubts about how good they are. Our conservatory is 20 years old and has a glass roof.

GD, by email

A: There are many firms marketing replacement insulated roof coverings for conservatories. I have not had any experience with any of them. The reason for the sudden appearance of so many of these products is a relaxation in the Building Regulations rules.

A conservatory was previously described as a room with at least 75 per cent of the roof and 50 per cent of the walls being glazed, and this exempted it from Building Regs control. This led to hundreds of thousands of home owners being sold cheap, glass boxes that were too hot in the summer and too cold in the winter. Under the new rules, you can replace your conservatory’s roof with something more substantial. Whether this is a good idea, however, is another matter.

Most conservatories are lightweight, insubstantial structures, with shallow foundations. They are largely built with timber frames that might now have areas of rot, or PVC-U frames using the cheapest, thinnest plastic sections. Both versions are liable to have cheap, badly made double-glazed windows that are now failing and misting up.

I am not sure that paying several thousand pounds to fit a new roof on top of such a flimsy structure would count as an “investment”.

FLOORED BY KITCHEN DAMP

Q: We live in an 1890s semi. The kitchen floor is concrete, and we are pretty sure it’s original. A cellar wall supports the inner kitchen wall, and that part of the floor is higher than the side by the kitchen door. We want to sort this before installing a new kitchen. We don’t think there is a damp-proof membrane – we have either damp or condensation patches under the lino we installed over the red tiles. We are worried that if we excavate the floor to lay a new one, we might undermine the house structure. What do you think? And if we go ahead, would you recommend solid concrete again or the beam and block option?

LE, London

A: It is unlikely that any of your walls will be built directly on to this concrete floor slab. The walls will have their own foundations, and the concrete would have been poured after the walls had been built. So digging up the concrete will not “undermine” the structure.

Victorian houses often had suspended timber floors throughout, but with a concrete and quarry-tile floor in the scullery. These are always cold and damp, as the Victorians did not expect the degree of comfort in a scullery that we now expect in our kitchen/dining rooms.

If possible, I would advise removing all the concrete, and replacing it with a suspended timber floor, insulated between the joists. Install airbricks in the rear outer wall, below floor level, to provide a through-flow of sub-floor ventilation for the whole house.

SHINE TAKEN OFF

Q: Can the shine be restored on PVC wood-effect window ledges damaged by sun and bird droppings?

DA, by email

A: No, but you can paint it. Some specialist PVC-U paints have disappeared from sale, but you can start with a coat of Dulux Difficult Surface primer, followed by traditional undercoat and gloss.